~ Brewing beer, computing, food, family, etc.

Arduino controlled Hot Liquor Tank: Part 1

A few months ago I set out to build some arduino controlled automated equipment to help me in my beer brewing process. As of a few weeks ago I have a working prototype. It is a Hot Liquor Tank that heats up to 15 gallons of water to a pre-set temperature and holds that temperature until the system is turned off. Since I made it to a the finish line of “Phase 1″ I decided now was a good time to document the project so that I don’t forget what I did, and hopefully, to offer some inspiration to others who see a problem and want to create something that fixes that problem.

I am planning to write about this project in three parts: Physical, Electronics, and Software.

Background

First, it might be helpful to give some background about brewing beer and the motivation for this project.

About 5 years ago I took up beer homebrewing as a hobby. It’s an interesting and satisfying activity that is simple and complex at the same time. Also, at the end you get beer.

Beer at it’s most basic is made from water, hops, yeast, and malted barley. In order to turn the starch in the malted barley into a sugar that the yeast are able to eat, brewers steep the grains in hot water. This is the fist step of ‘all grain’ brewing. The vessel you use to heat or hold the water is called a Hot Liquor Tank. The vessel that you steep the grains in is a Mash Tun.

Heating the water for this vital step is about as exciting as it sounds. On a typical brew day, I would get up at 6am on a weekend morning, go out to the garage and light the propane burner under a big pot of water that I had set up the night before. I would then get a cup of coffee and kill an hour while the water heated.

Inspiration struck when I saw two hackers from Detroit had built a Mind Controlled Flamethrower game. I read about their awesome build and realized that I could use a similar setup for automatically turn on a propane burner to heat water. I described my idea to my friend and he told me I could name the whole operation “The Exploding Brewery,” ’cause, you know, it would result in turning my garage into a fireball.

Taking my friend’s advise I started to to some research some alternative methods. Eventually I figured out that electricity, while still potentially dangerous, was a safer and more controllable option.

Physical HLT Build

I want to start out by giving some credit to the very talented people in the homebrew community. I could not have done any of this without advise and encouragement for the folks over at homebrewtalk.com. If anyone thinks I am breaking new ground here, I will point them to the DIY and Automation forums where some smart and talented folks have documented their projects.

Keg Cutting and Rust Removal

As I mentioned in a some earlier posts, I had a pretty tight budget. To save money, I got an old half barrel keg from a scrap yard and cut off the top with an angle grinder.

The keg cost me $30 at a North Philly scrap yard. If you don’t have access to an angle grinder (ask your friends and neighbors before you assume they don’t have one) you can get a cheap one for $20 from Harbor Freight, or borrow one from a local tool library.

I can’t stress enough that you need to observe safety precautions when you are using power tools. Safety goggles, earplugs and a face-mask are highly recommended. The procedure is pretty simple. Using the grinder and a cut off wheel, you cut around the top of the keg. Once the top is off, use a grinding wheel to take off the sharp edges and metal burrs. Finish off with a metal file and some sandpaper to get things down to a smooth finish.

There are a bunch of videos, tutorials and really good advise on this out there already, so I am not going to re-create those or give a bunch of advise. I have cut a keg exactly once. If anyone wants to know where to start, hit me up in the comments, and I will be happy to share some links.

When I finally got the top of the keg open I found spots of rust all over the stainless steel surface. Turns out that rust removal is not so bad if the metal is not pitted. Stainless steel is protected by a layer of chromium oxide that forms when it is exposed to air. Most stainless steel will not rust unless it is exposed to wet conditions for an extended period of time. I used some Barkeep’s Friend and a scrub pad to remove the rust. Then I rinsed and dried the inside of the keg thoroughly and let it sit in a dry place for a couple of days.

Hole Drilling (Also known as porting)

The next step was to drill holes for a valve to drain the tank and one for the electric hot water heater element . To do this I used a titanium coated step bit, a handheld power drill, and cutting oil to keep the bit and steel from getting hot.

If the metal gets too hot from the friction of the drill, you are hardening it and making it harder to cut. There are better bits than the cheap titanium ones.

There are weldless bulkhead kits to install the valves on most homebrew supply websites and often at your local homebrew shop. They come with instructions and are pretty easy to use. They cost considerably more, but if you are not planning on doing this often, then it might not be worth the extra money.

Electrical

To install and wire the hot water heater element I needed the following parts:

I also needed a multimeter, screwdriver, a drill, drill bits, files, and wrenches to put all of the parts together.

After drilling a 7/8″ hole for the element, I used a lock ring and silicon O-ring to get a water tight seal. The lock ring was screwed directly onto the element’s threads.

Before wiring the element, I needed to get the protective housing that would go around it ready. I then used a file to remove enough plastic so that the coupling matched the curved wall of the keg. I then spray painted the coupling and plug silver, because I did not like the way the white PVC looked. There was no need to do this, but I wanted to.

Using more epoxy, I attached the coupling to the side of the tank. After the epoxy was cured, I sealed the coupling with silicon caulk to make sure that it was water tight. The last thing was to drill a hole in the plug that the wire would fit snugly through, and run the wire through the hole before connecting the wire to the element.

I stripped the electrical wire and connected the black and white wires to the element’s screw posts. Using the JB Weld epoxy, I attached to ground wire directly to the outside wall of the tank. Looking back It might make more sense to attach an electrical connector or post to the tank so that you can remove the ground wire without too much hassle. I designed the system knowing that there was a good chance I would need to replace the element someday. It will be a pain to remove that epoxy connection.

Grounding is super important, because it will redirect any stray electrical current to the your household electrical system’s ground. It is also important that you have ground fault interrupt circuits in the outlet where you are going to plug the tank in. Make sure you have enough amperage on the circuit breaker you are plugging it into. To figure out if you are going to overload your circuit breaker, you will need some simple math: Watts = Amps * Volts. The Watts you get from your heater element (in this case 1650) and a standard North American electrical line is 110/120. I use used 120 to air on the side of caution even thought the element does not draw the 120. So in this case we have: 1650 = ? * 120. So you have a maximum of 13.75 amps. If you wanted to go with a 2000W heating element you would still only draw 16.67amps. This means if you have a 20A breaker on the circuit that you are plugging the equipment into, then you would not trip the breaker. I was happy with the 1650W because I wanted to plug a few other things into the circuit, as you will see in later posts. If you have no idea what I am talking about, you might want to do some reading before you decide to build something like this.

Unforeseen Problems

There were a few of problems with on the physical build that I did not anticipate. The first was heat insulation. It tuns out that if you heat liquid in a metal container to 180 degrees, the outside of that container is about 180 degrees. That makes it a little hard to touch it and means you are losing a lot of heat. My solutions was to to go to the local hardware store and get a hot water heater insulation blanket. I folded it over and cut a couple of holes for the drain and the power cord. I then had to seal any areas where water could get in with waterproof tape, so the fiberglass insulation between the plastic covered walls does not get wet. Water is a terrific way to turn your insulation into a heat conductor. Also it might get drippy and smell bad.

The other unanticipated problem was circulation the water. At first I thought that heating water would rise in the tank and make a gentle convection current and keeping all the water at about the same temperature. Turns out I was wrong on that one too. When I tested the system I got differences of as much as 20 degrees in different parts of the tank. Again it was time to do some research.

The DIYers all agreed that you needed a method of circulation. Some got motors and paddles on long rods to make mechanical agitators. I did some parts sourcing and figured out that it would take about a third to a half of my initial budget of $250 to buy the parts for an agitator. I started taking apart things with motors around the house, but it was looking like I would have to learn about gearing, torque and a whole mess of motor lore to do make a mechanical agitator. Then I would have to find some way to seal the whole thing to avoid contaminating my brew water with motor grease.

I turned to pumps, after reading that someone had used a submersible aquarium pump as an agitator. I wanted something food grade and did a lot of searching. I eventually found a really tiny food grade 6v pump. It was inexpensive, could handle temperatures up to boiling and was designed to run continuously. The downside was that the pump only moved one liter of water a minute, which is a trickle. I bought it anyway, and figured that if it was not enough, I could use it to build a fountain for the kids, or an automatic plant watering system. In the end, I was lucky. It ‘stirred’ the pot just enough so that there was less than a 1 degree difference in temperature all through the tank.

And at this point, I had a functioning electric HLT, although without any automatic controls just yet.

I hope you enjoyed this write up. I plan to the get the description of the electronics and software up in the coming weeks. Comments, questions and corrections are, as always, welcome.